Micro-fluid ejection devices, such as ink jet printers continue to evolve as the technology for ink jet printing continues to improve to provide higher speed, higher quality printers. However, the improvement in speed and quality does not come without a price. As ejection heads become more complex and include more ejection nozzles having smaller diameters, nozzle fabrication tolerances become more critical to the proper performance of the ejection heads.
Techniques for assembling micro-fluid ejection heads typically include applying a nozzle plate or nozzle plate and thick film layer to a substrate containing fluid ejection actuators on a device surface thereof. Manufacturing the parts separately and then assembling the parts to one another was a suitable manufacturing technique for relatively low tolerance, low speed ejection heads. Parts for making higher tolerance ejection heads are desirably assembled to one another before manufacturing for each of the parts is complete. For example, a first photoresist material may be applied to a substrate before it is imaged and developed to provide a thick film layer having flow features therein. Likewise, a nozzle plate made of a second photoresist material may be applied to the thick film layer before nozzles are imaged and developed in the nozzle plate. Use of the foregoing assembly technique may provide more accurate alignment between the flow features and ejection actuators on the device surface of the substrate.
Despite the use of photoimageable materials to provide the flow features in the thick film layer and the nozzles in the nozzle plate, there continues to be a problem with misdirection of fluid droplets ejected from the ejection heads. Accordingly, there continues to be a need for improved micro-fluid ejection heads and assembly techniques that provide a higher yield of usable ejection heads.
With regard to the foregoing exemplary embodiments of the disclosure provide a micro-fluid ejection head and methods for improving the fabrication and operation of the micro-fluid ejection head. The ejection head includes a photoimaged thick film layer attached to a substrate containing fluid ejection actuators. An orifice plate is laminated to the thick film layer. The orifice plate has a plurality of concentric orifices therein and is derived from a first photoresist material that is heated to a temperature sufficient to relieve film stresses in the photoresist material prior to exposing and developing the orifices in the orifice plate.
In another embodiment, there is provided a method for making a micro-fluid ejection head. The method includes applying a first photoresist layer to a device surface of a substrate containing fluid ejection actuators. A plurality of flow features are imaged in the first photoresist layer. The imaged first photoresist layer is then developed to provide a thick film layer including the plurality of flow features therein. A second photoresist layer is applied to the thick film layer. The second photoresist layer has a thickness ranging from about 2 to about 50 microns. Prior to imaging a plurality of nozzle holes in the second photoresist layer, the second photoresist layer is stress relieved. The imaged second photoresist layer is then developed to provide a photoresist nozzle plate on the first photoresist layer.
In yet another embodiment, there is provided a method for improving fluid ejection directionality from nozzles of a micro-fluid ejection head. The method includes applying a nozzle plate material to a thick film layer containing flow features on a substrate that includes fluid ejection actuators. The nozzle plate material is heated to a temperature sufficient to reduce stresses in the nozzle plate material without curing or flowing the nozzle plate material. Nozzles are then imaged and developed in the nozzle plate material.
An advantage of exemplary embodiments described herein is that the nozzles formed after stress relieving the nozzle plate material exhibit improved fluid ejection accuracy than nozzles made by techniques that do not include the stress relieving step. Other benefits of the disclosed embodiments may include improvements in adhesion and durability of the composite substrate and nozzle plate structure, and significant ejection head yield improvement.
For purposes of the disclosure, “difunctional epoxy” means epoxy compounds and materials having only two epoxy functional groups in the molecule. “Multifunctional epoxy” means epoxy compounds and materials having more than two epoxy functional groups in the molecule.